Document project processes
Add link other www.so/docs. Should be easy to adapt from: https://git.glasklar.is/sigsum/project/documentation/-/blob/main/archive/2023-09-05-sigsum-processes.md?ref_type=heads
Add link other www.so/docs. Should be easy to adapt from: https://git.glasklar.is/sigsum/project/documentation/-/blob/main/archive/2023-09-05-sigsum-processes.md?ref_type=heads